From: Andrea Arcangeli <aarcange@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>,
Marcel Apfelbaum <marcel@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] Default for phys-addr-bits? (was Re: [PATCH 4/5] x86: Allow physical address bits to be set)
Date: Wed, 22 Jun 2016 16:44:10 +0200 [thread overview]
Message-ID: <20160622144410.GL30202@redhat.com> (raw)
In-Reply-To: <ef002b40-712a-00e8-a30a-00057929a56f@redhat.com>
On Wed, Jun 22, 2016 at 04:33:18PM +0200, Paolo Bonzini wrote:
>
>
> On 22/06/2016 16:24, Andrea Arcangeli wrote:
> > Linux could not possibly crash instead if host phys bits > guest phys
> > bits because it will never depend on GPF triggering if the must be
> > zero bits of the guest pagetables are set. Linux won't ever try to set
> > those bits and I'd be shocked if any other OS does.
>
> Well, KVM does. It sets _all_ bits up to 51, not just one, but still we
> have a counterexample.
How can that crash? KVM doesn't use the host phys bits (or level1 host
phys bits), the bit to set is hardcoded up to 51 and assumed no host
would possibly fail at that.
The concern in the KVM case is for nested virt as it is for an host in
this regard.
The scenario you are concerned about only happens if the bit set is not
hardcoded to 51 but is in function of the host phys bits, which is not
what KVM does.
next prev parent reply other threads:[~2016-06-22 14:44 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-16 17:12 [Qemu-devel] [PATCH 0/5] x86: Physical address limit patches Dr. David Alan Gilbert (git)
2016-06-16 17:12 ` [Qemu-devel] [PATCH 1/5] BIT_RANGE convenience macro Dr. David Alan Gilbert (git)
2016-06-16 17:23 ` Paolo Bonzini
2016-06-16 17:24 ` Dr. David Alan Gilbert
2016-06-16 18:01 ` Peter Maydell
2016-06-16 18:05 ` Paolo Bonzini
2016-06-20 14:11 ` Dr. David Alan Gilbert
2016-06-20 14:17 ` Peter Maydell
2016-06-16 17:12 ` [Qemu-devel] [PATCH 2/5] x86: Mask mtrr mask based on CPU physical address limits Dr. David Alan Gilbert (git)
2016-06-16 19:59 ` Eduardo Habkost
2016-06-17 8:23 ` Dr. David Alan Gilbert
2016-06-17 12:13 ` Paolo Bonzini
2016-06-16 17:12 ` [Qemu-devel] [PATCH 3/5] x86: fill high bits of mtrr mask Dr. David Alan Gilbert (git)
2016-06-16 20:14 ` Eduardo Habkost
2016-06-17 7:47 ` Paolo Bonzini
2016-06-17 12:46 ` Eduardo Habkost
2016-06-17 13:01 ` Paolo Bonzini
2016-06-17 13:41 ` Eduardo Habkost
2016-06-17 14:25 ` Paolo Bonzini
2016-06-17 15:27 ` Eduardo Habkost
2016-06-17 15:29 ` Paolo Bonzini
2016-06-17 15:35 ` Eduardo Habkost
2016-06-17 13:51 ` Dr. David Alan Gilbert
2016-06-17 14:19 ` Paolo Bonzini
2016-06-17 8:53 ` Dr. David Alan Gilbert
2016-06-16 17:12 ` [Qemu-devel] [PATCH 4/5] x86: Allow physical address bits to be set Dr. David Alan Gilbert (git)
2016-06-16 17:26 ` Paolo Bonzini
2016-06-16 18:09 ` Eduardo Habkost
2016-06-16 20:24 ` Eduardo Habkost
2016-06-17 8:15 ` Dr. David Alan Gilbert
2016-06-17 8:43 ` Paolo Bonzini
2016-06-17 9:17 ` Gerd Hoffmann
2016-06-17 9:52 ` Igor Mammedov
2016-06-17 11:20 ` Gerd Hoffmann
2016-06-17 16:20 ` Laszlo Ersek
2016-06-17 16:07 ` Laszlo Ersek
2016-06-19 16:13 ` Marcel Apfelbaum
2016-06-20 10:42 ` Igor Mammedov
2016-06-20 11:13 ` Marcel Apfelbaum
2016-06-17 9:37 ` Dr. David Alan Gilbert
2016-06-17 9:54 ` Paolo Bonzini
2016-06-17 13:18 ` Eduardo Habkost
2016-06-17 13:38 ` Paolo Bonzini
2016-06-17 15:19 ` Eduardo Habkost
2016-06-17 15:28 ` Paolo Bonzini
2016-06-17 15:49 ` Eduardo Habkost
2016-06-21 19:44 ` [Qemu-devel] Default for phys-addr-bits? (was Re: [PATCH 4/5] x86: Allow physical address bits to be set) Eduardo Habkost
2016-06-22 12:41 ` Paolo Bonzini
2016-06-22 14:24 ` Andrea Arcangeli
2016-06-22 14:33 ` Paolo Bonzini
2016-06-22 14:44 ` Andrea Arcangeli [this message]
2016-06-22 14:48 ` Paolo Bonzini
2016-06-22 15:02 ` Andrea Arcangeli
2016-06-22 22:44 ` Michael S. Tsirkin
2016-06-22 23:23 ` Andrea Arcangeli
2016-06-22 23:45 ` Michael S. Tsirkin
2016-06-23 8:40 ` Gerd Hoffmann
2016-06-23 16:38 ` Michael S. Tsirkin
2016-06-24 5:55 ` Gerd Hoffmann
2016-06-24 23:12 ` Michael S. Tsirkin
2016-06-29 16:42 ` Dr. David Alan Gilbert
2016-06-30 6:10 ` Gerd Hoffmann
2016-06-30 10:59 ` Dr. David Alan Gilbert
2016-06-30 16:14 ` Gerd Hoffmann
2016-06-30 17:12 ` Dr. David Alan Gilbert
2016-07-01 19:03 ` Dr. David Alan Gilbert
2016-06-22 22:40 ` Michael S. Tsirkin
2016-06-22 23:15 ` Andrea Arcangeli
2016-06-19 3:36 ` [Qemu-devel] [PATCH 4/5] x86: Allow physical address bits to be set Michael S. Tsirkin
2016-06-20 7:04 ` Paolo Bonzini
2016-06-17 14:24 ` Marcel Apfelbaum
2016-06-16 17:12 ` [Qemu-devel] [PATCH 5/5] x86: Set physical address bits based on host Dr. David Alan Gilbert (git)
2016-06-17 7:25 ` Igor Mammedov
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